The present invention relates to nickel zinc ferrite and more specifically to a method of making monodispersed magnetic nanoparticles of nickel zinc ferrite.
Nickel zinc ferrite (NZFO) is useful in electromagnetic applications that require a high permeability, such as inductors and electromagnetic wave absorbers (Takanori Tsutaoka, J. App. Phys., 93 (5) 2789-2796 (2003), the entire contents of which are incorporated herein by reference). There is interest to make nanosized NZFO particles to reduce energy losses associated with bulk powders. Further, most electronic applications require the particles to be pressed into larger shapes with near theoretical density, which is difficult to obtain if the particles have a wide size distribution.
NZFO nanoparticles have been synthesized in a variety of methods including hydrothermal processing, mechanochemical processing, ceramic processing (i.e., solid state reaction) and a variety of solution chemistry methods. Using reverse micelle synthesis it is possible to form uniform size NZFO particles where the size can be tailored as well as its stoichiometry. Currently, there is not a reliable method for the processing of NZFO nanoparticles. In recent years, physical methods such as ball milling and chemical methods like hydrothermal synthesis have shown promise, but have fallen short of providing reliable single phase nanoparticles of NZFO where the size and chemical composition can be controlled. See, for example, Anderson Dias and Vicente Tadeu Lopes Buono, J. Mater. Res., 12 (12) 3278-3285 (1997); Albertina Cabanas and Martyn Poliakoff, J. Mater. Chem., 11, 1408-1416 (2001); Y. Tamura, T. Sasao, M. Abe and T. Itoh, Journal of Colloid and Interface Science, 136, 242-248 (1990); A. Dias, R. L. Moreira, Mater. Lett., 39, 69-76 (1999); Hyun J. Song, Jae H. Oh, Seung C. Choi and Jae C. Lee, Physica Status Solidi A, 189 (3) 849-852 (2002); P. C. Fannin, S. W. Charles, J. L. Dormann, Journal of Magnetism and Magnetic Materials, 201, 98-101 (1999); P. S. Anil Kumar, J. J. Shrotri, S. D. Kulkarni, C. E. Deshpande, S. K. Date, Mater. Lett., 27, 293-296 (1996); Adriana S. Albuquerque, Jose D. Ardisson, Waldemar A. A. Macedo, and Maria C. M. Alves, J. App. Phys., 87 (9) 4352-4357 (2000); and J. S. Jiang, L. Gao, X. L. Yang, J. K. Guo, and H. L. Shen, J. Mater. Sci. Lett. 18, 1781-1783 (1999), the entire contents of each are incorporated herein by reference.
Reverse micelle synthesis has been used in other oxide systems with considerable control over nanoparticle size and distribution. See, for example, M. P. Pileni, Crystal Research and Technology, 33, 1155-1186 (1998); J. Sims, A. Kumbhar, J. Lin, F. Agnoli, E. Carpenter, C. Sangregorio, C. Frommen, V. Kolesnichenko, and C. J. O'Connor, Molecular Crystals and Liquid Crystals, 279, 113-120 (2002); and Charles J. O'Connor, Candace T. Seip, Everett E. Carpenter, Sichu Li, and Vijay T. John, Nanostructured Materials, 12, 65-70 (1999), the entire contents of each are incorporated herein by reference. Briefly, reverse micelles are water-in-oil emulsions in which the water to surfactant ratio controls the size of water pools within which aqueous chemical syntheses take place, and consequently control the size resultant particles (J. Rivas, M. A. Lopez-Quintela, J. A. Lopez-Perez, L. Liz, R. J. Duro, IEEE Transactions on Magnetics, 29 (6) 2655-2657 (1993), the entire contents of which are incorporated herein by reference). This technique is particularly attractive for room temperature reactions such as the precipitation of oxide nanoparticles (Markus Lade, Holger Mays, Jorg Schmidt, Regine Willumeit, Reinhard Schomacker, Colloids and Surfaces A: Physicochemical and Engineering Aspects 163, 3-15 (2000), the entire contents of which are incorporated herein by reference). Synthesis of various nanoparticles within reverse micelles, specifically ferrites, has demonstrated the ability to control the particle size, size distribution (Charles J. O'Connor, Candace T. Seip, Everett E. Carpenter, Sichu Li, and Vijay T. John, NanoStructured Materials, 12, 65-70 (1999); and M. P. Pileni, A. Hammouda, N. Moumen, and I. Lisiecki, Fine Particle Science and Technology, edited by E. Pelizzetti (Kluwer Academic Publishers, Netherlands, 1996), p. 413-429; the entire contents of both are incorporated herein by reference), chemical stoichiometry, and cation occupancy (Everett E. Carpenter, Candace T. Seip, and Charles J. O'Connor, J. App. Phys., 85 (8) 5184-5186 (1999), the entire contents of which are incorporated herein by reference). However, previous work has often produced precursor particles that require subsequent firing (P. S. Anil Kumar, J. J. Shrotri, S. D. Kulkarni, C. E. Deshpande, S. K. Date, Mater. Lett., 27, 293-296 (1996); and Doruk O. Yener and Herbert Giesche, J. Am. Ceram. Soc., 84 (9) 1987-95 (2001), the entire contents of both are incorporated herein by reference).
The room-temperature synthesis of nanoscale NZFO ferrites that do not require further processing is disclosed herein. A surfactant system was employed for the room-temperature reverse micelle synthesis of NZFO nanoparticles. Sodium dioctylsulfosuccinate (AOT), was combined with a 2,2,4-trimethylpentane (isooctane) oil phase to make the reverse micelle solution. This allowed comparison to similarly produced materials from other research groups in which NZFO was synthesized in reverse micelles and subsequently fired to produce the desired product. The materials disclosed herein do not need a subsequent firing step. The reaction conditions of this system are optimized to produce, at room temperature, pure phase nanoscale NZFO particles over a narrow size distribution.